UNITRACC - Underground Infrastructure Training and Competence Center

Critical operating condition - condition 3

Critical operating condition - Condition 3

Results directly from condition 2a or also after longer down-times.
The excavation chamber is incomplete and the upper area is filled with water.
Danger: water enters the area of the spiral conveyor and causes liquid to muddy consistencies of the mud.
Pressure-balancing function of the spiral conveyor cannot be maintained.
Increased danger of crown collapse up to breaks into the open.

(Image: EPB …

May 18, 2020

Critical operating condition - condition 4

Critical operating condition - Condition 4

Results from a too low conveying performance of the spiral conveyor.
Solidification of the mud in interaction with the agitating of the cutting wheel, especially in and first in the central region, caused by the excessive pressure in the excavation chamber.
Consequence: sticking of machine parts up to down-time of the machine (condition 5).

(Image: EPB shield with compaction of the mud in the excavation …

May 18, 2020

Critical operating condition - condition 5

Critical operating condition - Condition 5

Resulting from condition 4 if the too low conveyor performance of the spiral conveyor is not immediately corrected.
With growing torque and reducing jacking speed the mud warms up increasingly.
Warming increasingly affects the solidification and sticking tendency.
In an extreme case the solidification reaches the entire excavation chamber starting from the centre of the excavation chamber.
Consequence: …

May 18, 2020

Critical operating condition - condition 6

(Image: Operating condition when encountering an obstacle (Condition 6) with reference to [Maidl97b] [Image: S&P GmbH])

Critical operating condition - Condition 6: Encountering an obstacle

When encountering an obstacle (e.g. a boulder), the contact pressure force must be increased.
Consequence: control and transfer of the required support pressure from the pressure bulkhead via the mud in the surrounding subsoil is immensely impaired.

(Image: EPB shield …

May 18, 2020

SM-V5 - working face with earth pressure support

May 18, 2020

Obstacle removal

Obstacle removal in partial excavation

(Table: Obstacle removal in pipe jacking with partial excavation [FI-Steina])

May 18, 2020

Obstacle removal

Obstacle removal in full-face excavation

(Table: Obstacle removal in pipe jacking with full-face excavation [FI-Steina])

May 18, 2020

Obstacle removal

Obstacle removal in special forms

(Table: Obstacle removal in pipe jacking (special forms))

May 18, 2020

Obstacle removal

May 18, 2020

(Image: Attention!)

If the method is changed, the principle of supporting the working face during jacking is changed. By doing so the technique-specific limits of application can be shifted and/or extended.

It is distinguished between:

unscheduled change of method by modification
schedules change of method by modification
scheduled change of method by conversion.

[Tunnel01]

In all cases, access is necessary for carrying out the required mechanical …

May 18, 2020

Unscheduled change of method by modification

Unscheduled changes of the method by means of modification are carried out from the pipe string or from a specially excavated auxiliary shaft.

(Image: Pros and cons)

Disadvantages of unscheduled changes of the method by modification:

the modification is labour-intensive and time-consuming (might take weeks)
causes high costs due to the delay of the construction project
ground stabilization measures might have to be taken

(Image: Attention!)

May 18, 2020

Scheduled change of method by modification

(Image: Attention!)

An expected or scheduled change of method technology must be taken into account early on in the planning phase.

If a modification in the shaft is not possible due to topographical or other reasons, then it is carried out in the protection of a specially built station through the pipe string [Tunnel01].

(Image: Pros and cons)

Disadvantages of scheduled change of method by modification:

modification is labour-intensive and …

May 18, 2020

Scheduled change of method by conversion

(Image: Attention!) A scheduled change of method by conversion can only be carried out with shield types that are further developed for this purpose.
(Image: Pros and cons) The advantages of scheduled change of method by conversion: conversion can take place in each spot of the jacking route relatively short conversion times if the subsequent material conveying does not have to be changed	(Image: Pros and cons) The disadvantage of scheduled …

May 18, 2020

Conventional changes of method by conversion

(Table: Conventional changes of method by conversion in pipe jacking [Tunnel01])

May 18, 2020

Change of method

May 18, 2020

Errors and consequences of damage

Damages in pipe jacking

In jacking processes, extensive and irreparable damages are frequently observed, which is due to irregularities of the subsoil.

Although extensive subsoil investigations can reduce the subsoil risk, failures and damages cannot be completely excluded.

(Image: Attention!)

These are the consequences of damages during pipe jacking:

Insufficient quality of the construction execution
Delay
High costs
Environmental impacts

May 18, 2020

Errors and consequences of damage

Damages in pipe jacking - statistics

(Image: Distribution of damages in pipe jacking in Germany (source: IFB, Hanover 1993))

May 18, 2020

Errors and consequences of damage

(Table: Damages that can occur in pipe jacking and their consequences [FI-Steina])

May 18, 2020

Errors and consequences of damage

May 18, 2020

NA-21 Utility Tunnelling: Pipe Jacking - Part 2

Today, the installation of gas, water and wastewater pipelines is still predominantly carried out using open trenches. In view of the numerous disadvantages associated with this method, it is imperative that trenchless pipeline construction be considered much more strongly in the future than it has been to date, as an alternative in the planning and construction of sewers and pipelines.

This module deals in detail with the numerous different types of shield machines, obstacle removal and possible errors in pipe jacking and their consequences.

After completing this module, you will have a sound knowledge of:

limitations of the use of shield machines and
errors and consequences of damage during pipe jacking.

Sep 14, 2005

Trenchless Technology for Installation of Cables and Pipelines

Manned techniques - pipe jacking

Definition

In these methods, jacking pipes [DINEN12889:2000] [ATVA125:1996] [Scher77a] [Stein85f] are jacked by pressing-in through the subsoil from a starting shaft to a target shaft with the aid of a jacking station or a main jacking station helped by intermediate jacking stations.

Jacking in a straight or curved line path is made possible by means of a steerable shield machine positioned at the head of the first pipe.

Operation and steering of the shield …

Sep 14, 2005

Trenchless Technology for Installation of Cables and Pipelines

Shield machines with partial excavation by hand (hand shields)

SM-T1 - working face with natural support

(Image: Open cowl shield with spiral conveyor for spoil removal and hydraulically extendable breast plate for gravel-sand soils without groundwater (external diameter 4280 mm) [FI-Eppin])

Natural support of the working face is always applicable when the existing subsoil is free of groundwater and the working face is a priori stable (working face without support) or is sufficiently supported by a self-forming earth wedge with a natural slope angle.…

Sep 14, 2005

Trenchless Technology for Installation of Cables and Pipelines

Shield machines with partial excavation by hand (hand shields)

SM-T2 - working face with partial support

With partial support, the surface of the working face is divided into sections and is either supported by means of natural partial support on bench plates (bench (plate) or platform shields) and/or by means of mechanical partial support using breast plates (Bild 9.2.1.1.2).

With bench shields, this division into sections has the purpose of reducing the length of the earth wedge and the size of the surface area of the slope [Scher77a].

Depending on …

Sep 15, 2005

Trenchless Technology for Installation of Cables and Pipelines

Shield machines with partial excavation by hand (hand shields)

Area of application of hand shields

The use of hand shields is recommended wherever very short jacking distances make the use of mechanical excavation uneconomic due to the high initial investment for the complex machine technology. In trenchless installation they are mainly used for crossing of traffic lanes and jacking distances of less than 50 m as well as for excavating special cross sections such as rectangular or arched profiles with manaccessible cross sections (Abschnitt 3).

Sep 14, 2005